(i) Field of the Invention
The present invention relates to an image reading apparatus, as well as a recording apparatus including the image reading apparatus.
(ii) Discussion of the Background
It is known to read images by a so-called sheet through method. In the sheet through method, a document is transported in a sub-scanning direction over a background reading apparatus. The reading apparatus includes a reading unit disposed at a fixed position. By this arrangement, the reading unit reads the portion of the document over the reading unit.
However, a contact glass of the reading unit may become contaminated with recording medium dust, because the document is transported over and contacts the contact glass. The contamination adversely affects the quality of the images read by the contact glass, which results in poor quality images formed a writing unit. Specifically, while contaminants on a contact glass of an image reading apparatus that does not use the sheet through method result in the formation of stray dots on an output copy, contaminants on the contact glass in an image forming apparatus that does use the sheet through method result in the formation of stripes on the output copy.
Known contaminants include floating contaminants and adhered contaminants. The floating contaminants include dust, recording medium powders and toner powders, while adhered contaminants are generally formed by deposition of toners from the document to the contact glass, since adhesives coated on the document are transferred to the contact glass when the document contacts the contact glass.
It is known to use a reading apparatus in which the image is read without permitting the document to contact the contact glass, to avoid adhesion of the adhesives and adhered contaminants on the contact glass. However, it is likely that the floating contaminants, such as the recording medium powders, will still settle on the contact glass and cause the quality of the images formed by the image forming apparatus to deteriorate.